The invention relates to a slide-like drive means and more particularly though not exclusively to feed and/or transport means comprising a housing with a cylinder bore for a piston, and a piston rod mounted on the piston and extending out of the housing.
Such feed devices have been proposed in the form of linear motors based on the use of hydraulic or pneumatic drive cylinders, in the case of which the power output is frequently at the end of the piston rod, that moves axially in and out of the cylinder. A mechanically reversed arrangement is however also possible in which a bush is moved by the cylinder and drives the load whereas the piston rod is stationary. As regards the point at which the unit is connected with the load, the designer has little freedom of choice with such arrangements. They further suffer from the disadvantage that the forces and moments act on the side of the piston-cylinder arrangement out of alignment with the center line of the piston rod. The driven piston rod or moving sleeve, respectively, will be displaced by one-sided loads to a certain extent so that parts are not precisely positioned. Because of the lack of lateral stability the seals of the piston and the piston rod are subjected to a high wear rate.
Furthermore pistons and piston rods are normally able to turn in relation to the cylinder. The driven piston rod or the moving sleeve is entrained by axial torques caused by the connection with the load so that the load is not steadied by a guide as would frequently be desired. The resulting rotary motion of the output drive part loads the seals of the piston and the piston rod. Although various devices have been proposed to prevent turning the cylinder actuators, they are elaborate, bulky and expensive to manufacture.
A further shortcoming experienced with known cylinder actuators is that their circular form makes it difficult to connect them with electronic or fluidic control components.